In an adaptive, multi-channel acoustic attenuation system, acoustic disturbances in an acoustic plant are sensed with error sensors, such as microphones or accelerometers, that supply an error signal to a multi-channel adaptive filter control model. The multi-channel adaptive filter control model is normally located in a centralized, electronic controller (i.e., a MIMO digital signal processor) having a central processing unit, memory, digital to analog converters, analog to digital converters, and input and output ports. In an adaptive active system, the adaptive filter control model supplies a correction signal to an active actuator or output transducer such as a loudspeaker or electromechanical shaker. The active actuator injects a cancelling acoustic wave into the acoustic plant to destructively interfere with the acoustic disturbance so that the output acoustic wave at the error sensors is close to zero or some other desired value. In an adaptive passive system, the adaptive filter control model supplies a correction signal to an actuator that adjusts a physical property of a passive component in the acoustic plant so that the acoustic disturbance at the error sensors is close to zero or some other desired value.
Adaptive acoustic attenuation systems often include multiple sensors and can include multiple active actuators and/or multiple adjustable passive components. Adaptive acoustic attenuation systems can use either feedforward or feedback adaptive control models. In feedforward systems, additional input sensors are needed to sense input acoustic waves and provide input reference signals to the channels of the adaptive filter model. A multi-channel adaptive filter control model typically adapts to model the acoustic plant to minimize the global cost function of the error signals from the error sensors. It is normally preferred that the channels in the adaptive filter control model either be intraconnected, or decoupled, as shown in U.S. Pat. No. 5,216,721 to Douglas E. Melton; U.S. Pat. No. 5,216,722 to Steven R. Popovich; and U.S. Pat. No. 5,420,932 to Seth D. Goodman. Allowed U.S. patent application Ser. No. 08/297,241, entitled "Adaptive Control System With A Corrected Phase Filtered Error Update" by Steven R. Popovich, filed on Aug. 25, 1994 discloses in FIG. 5 a MIMO adaptive control system in which the signals from the error sensors are filtered preferably to account for delays in phase changes due to the speaker error paths. These patents and the allowed patent application are assigned to the assignee of the present invention and are incorporated herein by reference.
Normally a distinct cable is required to connect each sensor, active actuator and/or passive component actuator to the centralized digital signal processor. In systems having a small number of sensors and/or actuators, or in systems where components are closely located to the digital signal processor, this type of star architecture and the number of distinct cables does not normally present a problem. However, in systems with numerous sensors and/or actuators, the number, weight and cost of cables can become a significant concern. U.S. Pat. No. 5,570,425, entitled "Daisy Chain" by Goodman, Eriksson et al., provides a central MIMO controller communicating through a control network that interfaces with sensor and actuator nodes to dispense with the need for providing separate cables from the centralized digital signal processor to each separate sensor and/or actuator. The network system shown in U.S. Pat. No. 5,570,425 discloses sensor and actuator nodes that may or may not include processing capabilities, but the overall system is governed by a centralized MIMO digital signal processor.
Data processing and data transmission requirements using a centralized digital signal processor can become extremely burdensome, especially as the number of sensors and actuators becomes large. In these large dimensional systems, input/output capabilities and computational processing requirements can exceed capabilities of a centralized digital signal processor. It is therefore desirable in some applications to decentralize adaptive filter processing, and eliminate the need for a centralized digital signal processor in a MIMO adaptive acoustic attenuation system.
U.S. Pat. No. 5,557,682 entitled "Multi-Filter-Set Active Adaptive Control System" by J. V. Warner et al., discloses several ways of interfacing two or more digital signal processors when it is necessary to increase either the input/output capabilities or processing capabilities of the system. U.S. Pat. Nos. 5,557,682 and 5,570,425 are assigned to the assignee of the present invention and are incorporated herein by reference. In general, the system must be reconfigured and software rewritten whenever sensors and/or actuators are added or deleted from the system. In high dimensional systems, this type of reconfiguration and software rewriting is not desirable.